Magneto



July 19, 1949.

v EVOLLENWEIDER MAGNETO Filed July so, 1945 6 R r s m a m h m m x m m w m I u /m l Z m 6 m E Patented July 19, 1949 UNITED STATES PATENT OFFICE 2,476,468 MAGNETO Emil Vollenweider, Sacramento, Calif. Application July 30, 1945, Serial No. 607,706

, 2 Claims. 1

This invention relates to, and it is an object to provide, an improved magneto for model airplanes, model racing cars, or the like; the magneto being of the direct drive type, as shown in my U. S. Patent No. 2,258,503.

Another object of theinvention is to provide a magneto, of the type described, which includes a novel timing mechanism; such mechanism embodying a minimum of parts, but accurately timing the engine explosions-as is necessary for high speed operation.

A further object of the invention is to provide unique means for mounting and aligning the magneto rotor on the projecting portion of the engine crankshaft.

A further object of the invention is to produce a simple and inexpensive magneto, and yet one which will be exceedingly effective for the purpose for which it is designed.

These objects are accomplished by means of such structure and relative arrangement of parts as will fully appear by a perusal of the following specification and claims. In the drawings similar characters of reference indicate corresponding parts in the several views.

Figure I is a side elevation of the magneto as mounted in connection with a model or midget engine.

Figure 2 is a. front end view of the magneto.

Figure 3 is a rear end view of the magneto.

Figure 4 is a sectional elevation of the magneto with the timing mechanism breaker points closed.

Figure 5 is a similar view, but with the breaker points open.

Figure 6 is a rear end view of the magneto rotor, detached.

Referring now more particularly to the characters of reference on the drawings, the numeral l indicates a model or midget engine of conventional type, such engine including a cylinder 2 into which a spark plug 3 is threaded at the top, a crankcase 4, and a forwardly projecting crankcase boss 5 through which the crankshaft 6 projects outwardly to a termination some distance ahead of the crankcase 4 The magneto comprises a substantially rectangular, vertical back plate 1 of light-weight but durable metal, perforated for additional lightness, as shown. Centrally the back plate I is formed with an attachment sleeve 8 which opens through said plate and is engaged about the crankcase boss 5. The sleeve 8 is split lengthwise with the split extending through the plate and between a pair of matching outwardly projecting ears 9 which extend integrally from said plate.

2 The cars 9 are connected by a tension screw I0. When the screw I0 is tightened the sleeve 8 friction-ally grips the crankcase boss 5 and prevents relative rotation of the back plate I.

The magneto is of the inductor type and includes an armature, indicated generally at II, mounted on the front of the back plate I by means of screws I2; the armature being of laminated steel and including field pieces I3 having transversely spaced depending legs I4 connected at their lower ends by a core I5. The core I5 is surrounded by an induction coil I 6 including primary and secondary windings as usual, such coil being wired in circuit, as will hereinafter appear.

An inductor rotor, indicated generally at IT, is mounted on the crankshaft 6 and is disposed for rotation between the field pieces I3, adjacent sides of the latter being symmetrical and relatively close to said rotor IT. The rotor I1 includes a circular rotor body I8 on which are secured opposed pole shoes I9. The pole shoes I9 are of soft iron, while the rotor body I8 is a permanent magnet formed of a high magnetic steel such as Alnico. Adjacent its axis the rotor body I8 is magnetically insulated from the crankshaft 6 by means of a bronze non-magnetic bushing 20. The bushing 20 includes a bore which tapers forwardly from its rear end, and a longitudinally grooved, split collar 21 wedgingly engages in said taper bore about the crankshaft 6, which not only accurately alines the rotor but secures the latter in place. If further securing means is necessary, a locking nut. or other device may be applied against the forward end of the rotor to prevent axial displacement thereof.

The timing mechanism of the magneto comprises a pair of cooperating breaker points 22 disposed generally to the rear of the device and below the attachment sleeve 8. The fixed one of the points 22 is mounted on a bracket 23 secured to the lower edge of the back plate I by means of a screw 24; said bracket being insulated from the back plate by an insulation assembly 2 5. The movable one of the breaker points 22 is fixed on the lower end of a spring finger 26 which extends upwardly behind the back plate I substantially tangentially of the attachment sleeve 8, said spring finger being secured in grounded relation to the rear end portion of one of the screws I2 by means of a nut 21. In line with the spring finger 26 the back plate I is formed with a horizontal bore 28 through which a plunger 29 slidably extends. The rotor body I8, on the back face thereof, is formed with an arcuate groove 30 of limited circumferential extent; the forward groove 30, said plunger advances under the influence of the spring finger and the breaker points close, remaining closed until the plunger rides j out of said groove. It will thus be seen that with rotation of the body 8 a recurring make and break of the points 22 is accomplished, producing the timing of the magneto and consequently the model engine. The rotor I1 is initially secured on the crankshaft 6 in proper position relative to the piston the engine I, to provide accurate timing.

The ignition circuit of the magneto comprises a pair of primary leads 31 and 32; the primary lead 31 being connected to a bracket 23 which carries the fixed breaker point 22, while the primary lead 32 is connected to one leg 14 of the armature. A high tension lead 33 extends from the coil I6 to the spark plug 3 of the engine.

The magneto as above described is extremely simple in its construction, particularly as to the timing mechanism, and consequently the weight of the device is reduced to a minimum. However, the timing mechanism is so constructed that it is effective in operation, and requires a minimum of maintenance or adjustment.

1 From the foregoing description it will be readily seen that there has been produced such a device as substantially fulfills the objects of the invention as set forth herein.

While this specification sets forth in detail the present and preferred construction of the device, still in practice such deviations from such detail may be resorted to as do not form a departure from the spirit of the invention, as defined by the appended claims.

Having thus described the invention, the following is claimed as new and useful and upon which Letters Patent is desired:

1. An inductor rotor for a magneto, said rotor comprising a substantially circular body of magnet steel, and a' pair of soft iron pole shoes secured n the body at opposed points; said pole 4 shoes having an arcuate outer edge, and a chordal inner edge, said inner edge of each pole shoe being afiixed to the periphery of said rotor centrally of the ends of said edge.

2. In a magneto which includes, with a driven shaft, a normally fixed back plate through which the shaft projects forwardly, a rotor mounted on the shaft in front of the back plate, and a fixed magneto part mounted on the face of the back plate in cooperative relation to the rotor; a plunger slidably extending through the back plate spaced from but parallel to the shaft, the

inner end of the rotor running close to the face of the back plate, said inner end of the rotor having a part-circle cam groove therein, the forward end of the plunger bearing aganist the inner end of the rotor in the circumferential path of said part-circle cam groove, a spring finger secured at one end on the rear of the back plate and engaged intermediate its ends by the adjacent end of the plunger, said spring finger urging the plunger toward the rotor, and a make and break ignition unit including one point on the free end of the spring finger and another cooperative point fixed relative to said back plate.

' EMIL VOLLENWEIDER.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,141,336 Hamm June 1, 1915 1,224,535 Hamm May 1, 1917 1,291,216 Smith Jan. 14, 1919 1,300,637 Oglesby Apr. 15, 1919 1,319,543 Watson 'Oct. 24, 1919 2,015,091 Spohn Sept. 24, 1935 2,060,260 Spengler Nov. 10, 1936 2,091,190 Tognola Aug. 24, 1937 2,213,724 Vogel Sept. 3, 1940 2,215,106 Lefebvre Sept. 17, 1940 2,258,503 Vollenweider Oct. 7, 1941 2,286,234 Scott June 16, 1942 2,315,902 Nowosielski Apr. 6, 1943 2,432,436 Morrill Dec. 9, 1947 FOREIGN PATENTS Number Country Date 21,273 Great Britain 1907 331,232 Great Britain July 3, 1930 

